Electric incandescent lamp



Dec. 2, 1958 F. s. LAMB 2,863,082

ELECTRIC INCANDESCENT LAMP 7 Filed Spt. 24. 1956 Invervtrcr: FT'ech ic|S. Lamb,

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United States Patent O ELECTRIC IN CAN DESCENT LAMP Frederick S. Lamb,Cleveland Heights, Ohio, assignor to General Electric Company, acorporation of New York Application September 24,1956, Serial No.611,577

4 Claims. (Cl. 313-278) My invention relates to electric incandescentlamps generally, and more particularly to lamps or similar deviceshaving a linear incandescible filament which is required to bemaintained under tension.

Various arrangements have heretofore been proposed for maintainingtension on elongated filaments to preserve the linearity of the filamentupon expansion thereof when heated to incandescence. However, in manycases the filament is free to vibrate laterally of its length therebyincreasing the apparent size or thickness of the light source or evenresulting in breakage of the filament.

It is an object of my invention to provide a simple but effective meanswhich will materially minimize lateral vibration of the filament andwill also rapidly dampen such vibration. It is a further object tominimize such vibrations without impairing the longitudinal tension onthe filament and without providing a sliding engagement with thefilament such as would lead to mechanical abrasion.

Briefly stated, these objects are attained by employing an arcuate orloop-shaped flexible spring member located in a plane approximatelytransverse to the length of the filament and having its ends fixedlysecured to spaced points on the filament supporting structure andconnected at approximately its midpoint to an end of the filamentwhereby to resist lateral movement of the filament but allowlongitudinal expansion and contraction thereof. The invention will bebetter understood by reference to the following detailed description andthe drawing wherein:

Fig. 1 is a perspective view of an incandescent lamp embodying theinvention;

Fig. 2 is a fragmentary elevation showing the spring arrangement forproviding tension on the filament and minimizing lateral vibration; and

Fig. 3 is a perspective view of a modified lamp structure embodying theinvention.

Referring to Fig. l of the drawing, the lamp illustrated thereincomprises an elongated tubular glass bulb or envelope 1 having a base 2at one end thereof. The end of the bulb is provided with a conventionalre-entrant stem 3 through which extends a pair of rigid lead-inconductors 4 and 5. The conductor 4 extends a short distance into thebulb whereas the longer conductor or stay member 5 extends substantiallythe fulllength of the bulb to its remote end and is rigidly maintainedin a fixed position by one or more transverse brace members 6. As hereinillustrated, the brace members are in the form of heavy wire loopsengaging the wall of the bulb and welded to the conductor 5, one at theremote end of the bulb and another adjacent the proximate end of thebulb near the stem 3. In some cases the brace 6 adjacent the stem 3 maybe omitted, par- 'At its remote end the filament is secured to a shortlength of lead wire 8 and is maintained under tension by suitableflexible spring means. As herein illustrated, the tension springs eachconsist of a closely coiled helix of tungsten-wire 9 secured fixedly atone end to the conductor 5 and at the other end to the lead wire 8.Since the springs 9 are in the electrical circuit through the filament'7 and conductor 5 they are made of wire of a size sutficient to preventoverheating upon flow of current therethrough so as to maintain theirresilience. In the cold or contracted position of the filament thesprings 9 are bent back to a reverse curvature so as to exert tension onthe filament even in its expanded position.

As thus far described the filament 7 is adequately maintained undertension. However, because of the long unsupported length of the filamentand its small diameter (.002 inch for instance) the filament is free tovibrate at right angles to its length, that is, normal to the planecontaining the filament 7, conductor 5' and springs 9. According to thepresent invention, such vibration is materially minimized andeffectively dampened by the provision of a supplementary vibrationspring member 10 connecting two points on the filament supportingstructure with the end of the filament. The

. spring 10 is a flexible wire member bent to an arcuate ticularly whenthe lamp is of relatively short length; on

the other hand, additional intermediate braces may be employed in lampsof longer length.

A filament 7 of straight tungsten wire is secured at one end to an endof the shorter lead-in conductor 4.

or openloop form having its ends secured fixedly by welding to spacedpoints on the adjacent brace 6 and connected approximately at itsmidpoint to the end of the filament through the lead wire 8 to which thespring is fixedly secured, preferably by welding. The spring 10 is thuslocatedapproximately in a plane transverse to the length of the filament7, As shown more clearly in Fig. 2 the said spring 10 is preferably bentback similarly to the springs 9 so it also exerts tension on thefilament. t i

In a preferred construction the spring 10 is a helical coil'of tungstenwire like the springs 9. However, each of the springs 10 and 9 mayalternately be constituted of a bundle of fine tungsten wires, forexample, about twenty-five strands of 6 mil wire.

When the lamp is subjected to shock or impact tending to cause thefilament 7 to vibrate laterally of the plane.

including the filament and the springs 9, such vibration is minimizedand is rapidly dampened by the flexible spring 10. It will be apparentthat this effect is obtained without adverse interference with thetensioning effect of the springs 9 and without the presence of anysliding contact with the filament such as would lead to abrasion. Whilethe spring 10 resists lateral vibration of the filament, it allowslongitudinal movement thereof. In fact, as mentioned above, it ispreferably so mounted that it supplements the tension exerted by thesprings 9 so that in some cases, as when the filament 7 is ofcomparatively short length, the springs 9 may be omitted and one or moresprings 10 may be employed to supply all the longitudinal tension on thefilament as well as the anti-vibration function.

The modified form of lamp shown in Fig. 3 is essentially like that shownin Fig. 1 except that the spring arrangement is located at the oppositeor base end of the lamp. Accordingly, the filament 7 is fixedly securedat the remote end of the lamp to a short length of conductor 11 whichconstitutes an extension of the conductor 5. The

proximate end of the filament is attached to the short sion of thefilament 7, it may be resiliently supportedat *bot-h'ends -by combiningthe spring arrangements shown in -Figs. 1 and -3. It will "also beapparent to those skilled in the art that various other modifications,substitutions or omissions may be made within the scope of'the-inventionwhileretaining the features and functions of the vibrationspring 10.

WhatI claim as new and desire-to secure by Letters Patent of the UnitedStates is:

1. An electric incandescent lamp comprising an elongated sealed bulb, afilament extending'longitudinally of said bulb,-and support means forsaid filament comprisingmeans to maintainlongitudinal tension on thefilament and to minimize lateral vibration and including a fiexiblespring member bent to arcuate form and located in a plane substantiallytransverse to the filament and having its ends secured fixedlytoportions of said supporting means, and means fixedly connecting thespring member at approximately its midpoint to one end of the filamentwhereby to dampen vibration of said filament in directions transverselyof its length while allowing longitudinal expansion and contraction ofthe filament.

2. An electric incandescent lamp comprising an elongated sealed bulb, afilament extending longitudinally of said bulb, and support means forsaid filament comprising-means to maintain'lo-ngitudinal tension on thefilament and to minimize lateral vibration and including a helicallycoiled flexible spring member bent to arcuate form and located in aplane substantially transverse to the filament and having its endssecured fixedly to portions of said supporting means, and means fixedlyconnecting the spring member at approximately its midpoint to one end ofthe filament whereby to dampen vibration of said filament in directionstransversely of its length while allowing longitudinal expansion andcontraction of the filament.

3. An electric incandescent lamp comprising an elongated sealed bulb, afilament extending longitudinally of said bulb, support means for saidfilament comprising a stay member extending longitudinally of the bulband a brace member secured to said stay member and extending laterallytherefrom into engagement with said bulb and means for resilientlysupporting said filanentunder tension from-said supportmeans andincluding a flexible spring member bent to arcuate form andlocated-in'a-plane-substantially transverse to the filament and havingits ends secured fixedly to spaced portions of said brace member, andmeans fixedly connecting said spring member at approximately itsmidpoint to one end of the filament whereby to dampen vibration of saidfilament in directions transversely of its length while allowinglongitudinal expansion and contractions of the filament.

4. An electric incandescent lamp comprising an elongated sealed bulb, afilament extending longitudinally of said bulb, support means for saidfilament comprising a stay member extending longitudinally of the bulband a brace member secured to said stay member and extending laterallytherefrom into engagement with said bulb and means for resilientlysupporting said filament under tension from said support means includinga plurality of flexible tension spring members extending laterally ofthe bulb and fixedly connected at respective ends to an adjacent end ofthe filament and to said stay member adjacent said brace member, saidtension spring members being flexible in directions both within andtransversely of the plane including said filament and tension springmembers, and a helically coiledvibration spring member bent to form anopen loop located in a plane substantially transverse to the filamentand having its-ends secured fixedly to spaced'portions of said bracemember, and means fixedly connecting said vibration spring member atapproximately its midpoint to the adjacent end of the filament wherebyto dampen transverse vibration of said filament.

References Cited in the file of this patent UNITED STATES PATENTS1,800,037 Wiegand Apr. 7, 1931 2,145,912 Anderson Feb. 7, 1939 2,425,864Cartun Apr. 19, 1947 2,425,865 Cartun Apr. 19, 1947 2,467,710 Vanttornet al Aug. 19, 1949 2,565,138 Leighton Aug. 21, 1951

